Raffinose Capped Silver Nanoparticles: A New Localized Surface Plasmon Resonance Based Sensor for Selective Quantification of Cr(VI) in Waste Waters

In this study, a new method for selective determination of Cr(VI) in water samples at pH 4 is presented using raffinose capped silver nanoparticles (Ag/Raff NPs) as an optical sensor. The method is based on the variation of LSPR absorption band intensity as a result of electrostatic interaction between the negatively charged Ag/Raff NPs and positive Cr(III) ions, in-situ produced by chemical reduction of Cr(VI) with ascorbic acid, combined with the fast kinetics of Cr(III) coordination to the –OH groups of the capping agent on the nanoparticle surface, further causing the nanoparticle aggregation. The calibration curve for Cr(VI) is linear in the range 2.5–7.5 μmol L−1, the limit of quantification achieved is 1.9 μmol L−1, and values of relative standard deviation vary from 3 to 5% for concentration level 1.9–7.5 μmol L−1. The interference studies performed in the presence of various metal ions show very good selectivity of Ag/Raff NPs toward Cr(VI) species. The added–found method is used to confirm the accuracy and precision of developed analytical approach.

Effect of Cellulose Reducing Ends on the Reinforcing Capacity of Powdered Cellulose in Polypropylene Composites

Powdered cellulose-reinforced (20 wt%) polypropylene composites were prepared by melt compounding and subsequent injection moldings. We assessed the effect of cellulose reducing ends on the capacity of powdered cellulose to reinforce polypropylene composites after seven days exposure to air circulation during the conditioning of samples. Tensile tests on the composites were performed at 5.08 mm/min. Fourier transform infrared spectroscopy revealed some changes that occurred within the composites by demonstrating a practical decrease in –C=O (1744 cm−1) absorption band intensity. A thermogravimetric analysis indicated differences within the thermal behavior of the prepared composites, showing a higher onset of degradation. Scanning electron microscopy of the fracture areas, together with load–extension curves, further characterized the development of interfacial cellulose/matrix adhesion as well as the brittle and ductile behavior of the composites. The results indicate that the thermal and tensile properties of powdered cellulose/polypropylene are improved by decreasing the amount of cellulose reducing ends in the system.

H 2 O−N 2 collision-induced absorption band intensity in the region of the N 2 fundamental: ab initio investigation of its temperature dependence and comparison with laboratory data

The present paper aims at ab initio and laboratory evaluation of the N 2 collision-induced absorption band intensity arising from interactions between N 2 and H 2 O molecules at wavelengths of around 4 μm. Quantum chemical calculations were performed in the space of five intermolecular coordinates and varying N−N bond length using Møller–Plesset perturbation and CCSD(T) methods with extrapolation of the electronic energy to the complete basis set. This made it possible to construct the intermolecular potential energy surface and to define the surface of the N−N dipole derivative with respect to internal coordinate. The intensity of the nitrogen fundamental was then calculated as a function of temperature using classical integration. Experimental spectra were recorded with a BOMEM DA3-002 FTIR spectrometer and 2 m base-length multipass White cell. Measurements were conducted at temperatures of 326, 339, 352 and 363 K. The retrieved water–nitrogen continuum significantly deviates from the MT_CKD model because the relatively strong nitrogen absorption induced by H 2 O was not included in this model. Substantial uncertainties in the measurements of the H 2 O−N 2 continuum meant that quantification of any temperature dependence was not possible. The comparison of the integrated N 2 fundamental band intensity with our theoretical estimates shows reasonably good agreement. Theory indicates that the intensity as a function of temperature has a minimum at approximately 500 K.

Infrared Study of Styrene-4-Methylstyrene Copolymers

Two types of crystalline syndiotactic polystyrene units are observed in these styrene- p-methylstyrene copolymers. The low-temperature crystalline form is observed in copolymers containing 2 weight percent or less 4-methylstyrene, and the high-temperature crystalline form is observed in copolymers containing 3 to 7 weight percent 4-methylstyrene. Quantitative analysis of styrene-4-methylstyrene copolymers can be performed with the use of infrared spectroscopy and an infrared absorption band intensity ratio technique.